Method and apparatus for injecting oil into the tuyeres of a blast furnace

ABSTRACT

A method and an apparatus for injecting oil into the tuyeres of a blast furnace preferably if the substitution ratio is above 50 to 100 kg oil/ton of pig iron. The oil is injected into the blast current with a speed at which it is not atomized when leaving the nozzle but injected as coherent jets, preferably in radial direction, maintaining their coherence a substantial distance in front of the nozzle. In this way the combustion of the oil is improved and its utilization can be increased to far greater amounts of oil which can be economically injected into the blast furnace in substitution of coke.

United States Patent 1191 Luth [ 51 Sept. 3, 1974 METHOD AND APPARATUSFOR INJECTING OIL INTO THE TUYERES OF A BLAST FURNACE [21] Appl. No.:191,451

[30] Foreign Application Priority Data Oct. 21, 1971 Germany 2051676[52] US. Cl 75/41, 75/42, 266/41, 266/29, 239/425, 239/431 [51] Int. ClC21b 5/00 Field of Search 266/41, 29, 30; 239/425, 239/426, 430, 431;431/4, 8, 187; 75/41, 42,

[56] References Cited UNITED STATES PATENTS 290,343 12/1883 Morgan etal. 75/42 1,393,749 10/1921 Carstens r. 266/29 X 1,511,019 10/1924B1uemel 431/187 2,175,517 10/1939 Ditto 75/41 2,965,163 12/1960 Lange etal 239/425 X 3,154,134 10/1964 Bloom 239/431 X 3,197,305 7/1965 75/423,207,597 9/1965 Hashimoto et a1 75/42 Primary Examiner-Carroll B.Dority, Jr. Attorney, Agent, or Firm-Holman and Stern 5 7 ABSTRACT Amethod and an apparatus for injecting oil into the tuyeres of a blastfurnace preferably if the substitution ratio is above 50 to 100 kgoil/ton of pig iron. The oil is injected into the blast current with aspeed at which it is not atomized when leaving the nozzle but injectedas coherent jets, preferably in radial direction, maintaining theircoherence a substantial distance in front of the nozzle. In this way thecombustion of the oil is improved and its utilization can be increasedto far greater amounts of oil which can be economically injected intothe blast furnace in substitution of coke.

9 Claims, 3 Drawing Figures METHOD AND APPARATUS FOR INJECTING OIL INTOTHE TUYERES OF A BLAST FURNACE BACKGROUND OF THE INVENTION The inventionrelates to a method of adding fuel oil to a blast furnace, in which fueloil is added to the stream of combustion air supplied by a tuyere, andto a device for carrying out this method.

It is known that the introduction of fuel oil instead of coke into theblast furnace is effected by spraying the fuel oil into the furnaceblast, i.e. the combustion air supplied to the blast furnace, and thistakes place inside the tuyeres.

However, the economics of adding fuel oil are considerably limited,because above a certain amount of oil, generally above 50 to 100 kgoil/ton of pig iron, the substitution ratio, i.e. the amount of cokeeffectively replaced by the addition of oil falls from 1.5 to under 1.0and below, and at the same time a thick black smoke occurs, which causesthe undesirable settlement of soot coming from the fuel oil in the fluedust collector. This flue dust means wasted fuel.

Attempts have already been made to increase the amount of oil which canbe added economically, by the addition to the fuel oil of additives, butthis has had only limited success. Also a better atomization of the oilsupply jets, which previously blew practically solely as a spray intothe blast current, did not have the desired success. However, on theother hand, a spraying of this type, i.e. the addition of fuel oil tothe furnace blast in the form of an oil spray of fine little droplets,which forms immediately before the oil jet, was not successful even ifthe oil supply jets had a radial direction component when being sprayedinto the blast current. This is because the blast current has acomparatively high viscosity which is nearly the viscosity of the oiland the oil spray cannot be homogeneously distributed over a broadportion of the cross-section of the tuyeres ready to be completelyburned just in the mouth of the tuyere. In the prior art method ofinjecting the oil as a spray the oil spray is compressed within thecentral area of the tuyeres and cannot be completely burned on its wayout of the tuyere within about 500 microseconds between the moment ofinjection until passing the mouth area of the tuyere. Thus, only afractional burning is achieved which is not complete and reduces the oilonly to soot without heating effect, assuming more than 50 to 100 kg oilper ton of pig iron are added to the blast.

SUMMARY OF THE INVENTION Despite an addition of fuel oil of up to aboutlOO kg oil/ton of pig iron or more, it is the object of the invention toobtain a favourable substitution ratio and thus to avoid the formationof thick black smoke, i.e. unnecessary losses by way of soot.

It is also an object of the invention to achieve a broad and improvedhomogeneous distribution of the substituted oil over the cross-sectionof the blast current within the tuyeres.

It is a further object of the invention to improve the injection of oilinto the blast current by changing the manner of the injection of theoil and finding an advantageous ratio of the injecting speed of the oilin relation to the speed of the blast current.

Moreover it is an object of the invention to improve the construction ofthe nozzles injecting the oil into the blast current.

Surprisingly, according to the invention it has been found that this canbe achieved if the oil is injected into the tuyere blast from thelongitudinal centre of the tuyere in radial direction to the tuyere orat about right angles to the flow of the tuyere blast by means of atleast one oil jet. There results an optimum economy, if up to 15 percentby weight, preferably up to 10 percent by weight of water or of watervapour is added to or injected with the oil.

In this case, the injection of the oil in radial direction should beunderstood to mean that the oil is injected and distributed over aconsiderably wider crosssection across the blast current than in theknown methods. Moreover, by injection of the oil jet it is meant thatthe oil jet leaving the oil nozzle is not atomized into an oil spray ordisintegrated into fine droplets by the blast immediately in front ofthe nozzle (as it is the case if the speed of the oil when leaving thenozzle is to low in comparison with the speed of the blast current), butthe coherency of each oil jet is largely maintained to a greaterdistance in front of the nozzle, in order to achieve a maximumdistribution of fuel oil across the blast current. Only in this way isit possible to distribute the fuel oil as widely as possible across thefurnace blast, which at approximately l,250 1,300 C has a comparativelyhigh viscosity. On the basis of the wide distribution of the fuel oilaccording to the invention the disadvantage of the need of excessivelymore fuel is avoided which can result due to lowering the hearthtemperature of the blast furnace. This considerably improveddistribution of fuel oil is assured with the method according to theinvention especially inside the tuyere or shortly in front of itsorifice, since the possibility of any mixing ocurring deeper in thehearth is limited on account of the relatively high viscosity of theflue gases in the blast furnace. In order to keep the oil jets compactto as far as possible in front of the oil nozzle, it is essential thatthe injection of the fuel oil takes place at a comparatively highinjection speed of at least 20 m/sec compared with the ten times asgreat (200 m/sec) speed of the furnace blast. In this way the oil jetsatomise only when there is an additional increase in their speed due tothe blast speed, so that their reaction with oxygen occurs after a truemixing reaction, which is increased widely over the cross-section of theblast current.

The value of 20 m/sec for the injection speed of the oil depends,however, on the individual operation conditions of the furnace. Thus,the scope of the invention includes all such normal variations.

Despite the cooling as a result of cracking or cleavaging of the fueloil caused initially with this fuel oil injection according to theinvention, which cooling is also shifted in radial direction, if thetemperature increase of the tuyere walls is too high under certaincircumstances it can be further reduced by the addition of water vapouror preferably of water to the fuel oil. Thus, in addition to the effectof the water vapour or superheated steam as a combustion accelerator,there is also the cooling effect which occurs when it is added to fueloil distributed in a considerably uniform manner over the entirecross-section of the tuyere.

Since the method according to the invention is based substantially on abetter radial distribution of the fuel oil injection, the advantagesobtained therewith can also be obtained if the oil is injected radiallyand diagonally against the blast flow.

Similarly, with a different construction of the tuyeres an oil injectiondistributed uniformly over the tuyere cross-section by means of aninjection undertaken from the periphery of the tuyere and occurringradially inwardly, can have advantages, although injecting the oil inradially outwardly direction is much more preferred.

A preferred, advantageous execution of the method is achieved with adevice or an oil injection nozzle lance, whose nozzle tip is located inthe vicinity of the longitudinal centre of a tuyere and which ischaracterised according to the invention in that the nozzle tip hasseveral nozzles distributed over its periphery and directed in radialdirection to the tuyere or in a direction with a considerable radialcomponent or at a steep angle to the tuyere flow.

Thus, the individual oil nozzles preferably having a certain length injeting direction can start from a central distribution chamber, in whichthere is located an oil-flow nozzle directed in axial direction, infront of which an eddy chamber is provided so that inside thedistribution chamber a turbulence of the oil/water or steam mixtureoccurs.

Such a cooling of the oil injection lance is essential for theoperation, because the high temperature of the furnace blast formerlyled within a few seconds to a decomposition of the fuel oil within thelance and thus to a clogging of the oil nozzle.

With an axially elongated distribution chamber, the individual nozzlescan be distributed over a greater axial length, whereby instead of onlya relatively flat, radial injection plane, an axially extended injectionzone can be formed, in which the individual nozzles can additionallyinject with varying injection angles. Thus the longitudinal axes of theindividual nozzles or their injection directions can intersect, so thatthe turbulence and atomization of the fuel oil, when having reached theradially outward area of the cross-section of the tuyere, is increasedby mutual kinetic interference of the oil outlet jets. With axiallydistributed nozzles the lance tip is longer, so that no additionalobstruction of the free cross-section of flow in the tuyere occurs. Withthe distribution of the nozzles axially over the lance head theindividual nozzles can also be arranged offset in their anglerelationship.

An additional cooling of the front end of the oil injection lance isachieved if the oil flow leaving an oil flow nozzle into the eddychamber is directed against the inner surface of the front end of thedistribution chamber in the blast direction.

Moreover the simple construction of the oil injection la'nce accordingto the invention allows a construction with which it can be exchangedeasily and quickly in the tuyere.

The features according to the invention are moreover not limited toblast furnaces, but may be applied for all similar purposes.

The invention is described in detail in the following in variousembodiments with reference to the drawings.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic longitudinalsectional view of the oil injection according to the invention insidethe tuyere of a blast furnace.

FIG. 2 is an enlarged longitudinal sectional view of a nozzle tipaccording to the invention; and

FIG. 3 is a schematic view of a modified nozzle tip having nozzleslocated in three different angular positions.

DETAILED DESCRIPTION OF INVENTION According to FIG. 1 a nozzle lance 10,having an internal diameter of, for example, approximately 6 8 mm,projects, for example, into a water-cooled tuyere 11, through whichthere is injected into the hearth of a blast furnace the furnace blast12 pre-heated, for example, t o l,000 C or more, having a speed, forinstance, of 200-320 m/sec. The supply of oil 13 is effected by means ofthe nozzle lance 10. Supply pipe 15 admits measured amounts of water orsteam 16 passing from needle valve 14 to lance 10. The amounts of wateror steam 16 varying according to the method of operation of the blastfurnace, which is already available for the indispensable pre-heating ofoil having, for example, a pressure of 6 atmospheres. The added amountof water or steam can always be regulated in a different manneraccording to the method of operation of the blast furnace.

Generally, up to 15 per cent by weight of water or water vapour issufficient relative to the amount of oil. However, in normal conditions,optimum efficiency lies in the addition of up to 10 per cent by weightof water or steam, whereby the increase in temperature, which isnormally involved with the addition of oil can be stabilized.

The fuel oil 13 is injected through the nozzle tip, into the blaststream transverse to the direction of the flow at approximately (arrowa). The oil injection direction according to the arrows shownschematically in FIG. 1 can also deviate a certain amount from the 90-radial direction, either forwards (arrow b) or backwards (arrow 0). Thenozzle lance 10 or the nozzle tip 1 do not have to be located exactlyco-axial the longitudinal central axis L, but can lie off-centrecorresponding to the optimum direction of flow of the furnace blast.Moreover there can also be provided several nozzle tips 1 distributedradially.

The nozzle tip illustrated on an enlarged scale in FIG. 2 is releasablyconnected at 7 to the lance 10 and has a number, for example 6, 8 up to12, of individual nozzles 2 directed radially outwardly, having adiameter, for example, of 3 mm and a noticeable length of bore. Througheach tuyere and nozzle tip approximately 260 kg of fuel oil can beinjected, at approximately 3 atmospheres excess pressure in the nozzlelance 10 with respect to the blast pressure, and a viscosity of 15 cSthaving an outlet speed of approximately 20 25 m/sec. The distance of thenozzle tip 10 from the front tuyere aperture amounts to, 250 mm forexample, with an average diameter of the tuyere of 200 300 mm.

The nozzle tip 1 has a central distribution chamber 3, from which thenozzles 2 start and into which an oil flow nozzle 4 can project, whichsupplies the oil 13 to the front end 6 of the distribution chamber 3 sothat this end can be cooled. In front of the oil flow nozzle 4 there isthus set up simultaneously an eddy chamber 5, from which the oil 13 isinjected out through the nozzles 2.

An axially extended nozzle tip 1a, according to FIG. 3 can also be usedin which the fuel oil reaches the furnace blast 12 by means of aninjection region 17 extending in axial direction of the tuyere. Withthis, the injection angle of the individual nozzles can also be directedobliquely according to the arrows d, e and f in FIG. 3, in particularobliquely or inclined to each other, so that at the same time as themore regular distribution of the oil supply over the tuyere crosssectionthe atomization followed subsequently to the distribution is improved.Moreover the front set of nozzles respectively can have an injectiondirection which can be directed backwards, in order to compensate forthe effect in the speed of the blast. At any rate, every injected jet ofoil first has a radial path which on the way radially outward is similarto a parabolic curve which is changed at about two-thirds of the innerradius of the tuyere outward to the axial direction. The initial speedof the oil is calculated such that the oil jets do not contact the innerwalls of the tuyeres. The desintegration or atomization of the jet beamsstarts approximately in the area at which their direction is turned tothe axial direction.

The oil supply can be regulated by changing the supply pressure, but abetter way is to replace the nozzle tips 1. Nozzle tips for differenttotal amounts of oil to be injected can be kept available for 50 kgoil/h or 60 kg oil/h etc, so that the optimum injection characteristicsare attained at the time of changing the total of the oil supply.

A further possibility for improving the uniformity of the fuel oilinjection, lies in forming the diameter of the individual nozzles in adifferent manner systematically so that, for example, one set of nozzlescovers a narrow injection area and another set of nozzles covers anouter injection area.

Finally, the uniformity of the fuel oil injection can be attained by theangularly staggered arrangement along the periphery of the nozzle tip 1of two axially spaced sets of nozzles.

With the method and apparatus according to the invention it is possibleto achieve a comparatively high specific heat capacity for each tuyere,which capacity considerably exceeds the value of l Gcal/liter space ofthe tuyere, which value in the known art up to now was regarded as amaximum limit. This is achieved without .having additional amounts ofsoot.

What is claimed is:

l. A method for injecting more than 50-100 kg fuel oil/ton of pig ironinto a blast furnace or the like comprising the steps of passingcombustion air at a temperature of about 1,000C through a tuyere havinga longitudinal axis and a smooth continuous inner wall having afrusto-conical shape becoming smaller in cross section in thedirectionof the combustion air flow; positioning at least the nozzle ofan oil lance along the axis of said tuyere, which oil lance has aplurality of nozzles about the circumference of the lance, the axis ofeach nozzle being generally directed radially outwardly introducing upto percent by weight of water to the fuel oil; then injecting a streamof liquid oil and water through the nozzles generally radially outwardlytowards the inner wall of the tuyere at an exit speed relative to thespeed of the combustion air passing through the tuyere of approximatelya ratio of 1:10 such that the injected oil and water remains a coherentstream until it has traveled the majority of the distance to the innertuyere wall at which time it atomizes thereby achieving a greaterdistribution of oil in the combustion air of a tuyere.

2. The method as claimed in claim 1 wherein the exit speed of the fueloil is at least 20 m/sec.

3. The method as claimed in claim 2 wherein the exit speed is 25 m/sec.

4. The method as claimed in claim 1 wherein the nozzle is positionedfrom the exit of the tuyere along the longitudinal axis of the tuyere adistance approximately equal to the diameter of the tuyere.

5. The method as claimed in claim 1 wherein the water is in the form ofsteam, 10 percent by weight is introduced, and the steam condenses toliquid after it is introduced into said fuel oil.

6. The method as claimed in claim 1 wherein some of the radial nozzleaxes being at a angle to the longitudinal axis and other of the radialnozzle axes, spaced downstream said 90 angle axes being inclined towardsthe direction of flow of the combustion air so that the coherent streamsof oil injected through the nozzles impinge at a radial distance fromthe lance which augments the atomization.

7. The method as claimed in claim 1 wherein the oil stream remainscoherent following a parabolic curve until about two-thirds of theradial distance from the nozzle exit to the inner wall of the tuyere hasbeen traversed at which time the stream is atomized.

8. Apparatus for injecting fuel oil into a blast furnace or the likecomprising a tuyere having a longitudinal axis and a smooth continuousinner wall; an oil lance positioned along the axis of said tuyere; a capon the end of the oil lance and an oil flow nozzle of graduallydecreasing cross-section axially upstream said end so as to form an eddychamber between the end of the cap and the oil flow nozzle; and at leastone nozzle in the wall of the eddy chamber which nozzle has an axisdirected radially outwardly so that the oil flows through the oil flownozzle directly impinging against the end of the cap to cool same,changes direction in the eddy chamber and exits from the nozzle in acoherent stream.

9. Apparatus as claimed in claim 8 wherein there are a plurality ofnozzles in the wall defining the eddy chamber; a first set of nozzlesare arranged about the circumference, their axes being 90 to thelongitudinal axis; a second set of nozzles arranged about thecircumference intermediate said first set and the end of the cap, theaxes of said second set being inclined upstream the gas flow in thetuyere so that the coherent streams of oil issuing from the second setof nozzles impinges the coherent streams of oil issuing from the firstset at a radial distance from the nozzle exits to augment theatomization of the oil.

Dated September 3, 1974 Patent No. 3833356 Inventor s) Fr'iedr ichAugust K! r 1 Lgth .It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

[30] Foreign Priority Data:

German Appln. P 2051676.l filed October 21, 1971 [75] Inventor:

Friedrich August Karl L i th Signed and sealed this 21st day of January1975.

(SEAL) Attest: MCCOY M. GIBSON JR. c. MARSHALL DANN Y Attesting OfficerCommissioner of Patents FORM PC4050 (IO-69) uscoMMdDc 603754569 1! ussovnmhn'r manna omc: no: o-au-au,

2. The method as claimed in claim 1 wherein the exit speed of the fueloil is at least 20 m/sec.
 3. The method as claimed in claim 2 whereinthe exit speed is 25 m/sec.
 4. The method as claimed in claim 1 whereinthe nozzle is positioned from the exit of the tuyere along thelongitudinal axis of the tuyere a distance approximately equal to thediameter of the tuyere.
 5. The method as claimed in claim 1 wherein thewater is in the form of steam, 10 percent by weight is introduced, andthe steam condenses to liquid after it is introduced into said fuel oil.6. The method as claimed in claim 1 wherein some of the radial nozzleaxes being at a 90* angle to the longitudinal axis and other of theradial nozzle axes, spaced downstream said 90* angle axes being inclinedtowards the direction of flow of the combustion air so that the coherentstreams of oil injected through the nozzles impinge at a radial distancefrom the lance which augments the atomization.
 7. The method as claimedin claim 1 wherein the oil stream remains coherent following a paraboliccurve until about two-thirds of the radial distance from the nozzle exitto the inner wall of the tuyere has been traversed at which time thestream is atomized.
 8. Apparatus for injecting fuel oil into a blastfurnace or the like comprising a tuyere having a longitudinal axis and asmooth contInuous inner wall; an oil lance positioned along the axis ofsaid tuyere; a cap on the end of the oil lance and an oil flow nozzle ofgradually decreasing cross-section axially upstream said end so as toform an eddy chamber between the end of the cap and the oil flow nozzle;and at least one nozzle in the wall of the eddy chamber which nozzle hasan axis directed radially outwardly so that the oil flows through theoil flow nozzle directly impinging against the end of the cap to coolsame, changes direction in the eddy chamber and exits from the nozzle ina coherent stream.
 9. Apparatus as claimed in claim 8 wherein there area plurality of nozzles in the wall defining the eddy chamber; a firstset of nozzles are arranged about the circumference, their axes being90* to the longitudinal axis; a second set of nozzles arranged about thecircumference intermediate said first set and the end of the cap, theaxes of said second set being inclined upstream the gas flow in thetuyere so that the coherent streams of oil issuing from the second setof nozzles impinges the coherent streams of oil issuing from the firstset at a radial distance from the nozzle exits to augment theatomization of the oil.